Fuse



y 1946' I H. c. HEBARD 2,400,002

FUSE

Filed April 24, 1942 2 Sheets-Sheet 1 ATTORNEYS f i j H. c. HEBARD FUSE Filed April 24, 1942 ATTORNEYS Patented May 7, 1946 U ITED FUSE Hugh Charles Hebard, Northwood, England Application April 24, 1942, Serial No. 440,374 In Great Britain March 3, 1941 1 Claim.

This invention relates to aerial bombs, projectiles and the like and has for its object to provide an improved safety arming device designed to prevent premature explosion of a bomb or projectile, for example, when being loaded on to an aircraft or after release therefrom.

According to the invention in a bomb or projectile fitted with a fuse of the type comprising a spring-loaded striker arranged to impinge upon a detonator cap, the said striker is normally restrained from operation by a Wedging device which isadapted to be released by wind-operated means after the bomb or projectile has been released or discharged for operation.

Reference will now be made to the accompanying drawings which illustrate by way of example a construction according to the invention and wherein:

Fig. l is a sectional elevation of part of an aerial bomb showing the safety arming device in the safe position, that is, with the striker locked in the inoperative position,

Fig. 2 shows the safety arming device in an intermediate position and Fig. 3 shows the safety arming device in the release position and the striker in engagement with the detonator cap.

Referring first to Fig. 1, the device shown comprises a striker a movable within a casing I) under control of a spring and adapted to detonate a cap or cartridge (1 by means of which the main charge of the bomb is ignited either directly or through a delayed action fuse. The striker a is carried by a stem e the outer end of which is screwed or otherwise attached to a sleeve ,f also movable axially in the outer end of the casing 12. The sleeve is formed with a series of apertures g in which a number of steel balls h is supported, said balls engaging externally an inclined seating 1' formed on the outer end of the casing b, and being held in engagement therewith by a tapered pin 7' extending axially into the sleeve from its outer end. The pin 7' is normally maintained in the safety position in which the balls prevent axial movement of the sleeve ,f. by a screw k which bears upon the butt end of the pin said screw being supported in a cap I mounted on the outer end of the casing. The screw is is adapted to be rotated by a wind vane m which may be attached directly to the screw but preferably drives the screw through a lost motion connection constructed as follows: The wind vane m is mounted upon a hollow hub n into which the outer end of the screw 70 extends axially, the said hub having an apertured end wall n in screw-threaded engagement with the screw. A head k on the screw limits outward movement of the hub upon the screw; 'Thus during the initial rotation of the wind vane said vane merely rotates around the screw but after the hub wall n contacts the head of the screw the continued rotation of the vane turns and lifts the screw thereby releasing the tapered pin 7.

It will be understood that with the wedging device above described there is a critical angle of friction for the wedge, that is, the tapered pin in which the whole system is in limiting equilibrium, and taking this factor into consideration the arrangement according to the invention can be designed to operate in either of two ways.

In the first'case, the wedge angle is made slightly greater than the critical angle so that the pressure of the striker spring 0, acting on the balls it through sleeve f. causes the balls by reaction against the inclined seating i to squeeze out the tapered pin a as the retaining device k is gradually unscrewed by the wind vane. Thus as soon as the screw k reaches the release positionthe tapered pin has been moved sufiiciently to allow the balls to clear the inner edge of the seating 2', whereby the sleeve will be free and the striker will be impelled into contact with the detonator by spring 0. This arrangement makes possible the use of a relatively small wind vane and is readily adapted for the ignition of a delayed action fuse by air pressure. It will be understood that the squeezing out of the tapered pin is caused by the vertical component of the pressure exerted by the balls on the wedge surface of the pin, and that this component is quite small in value relatively to the spring pressure when the wedge angle is only slightly greater than the critical angle, although it rises rapidly as it increases beyond that point. Therefore, when the angle is only slightly greater, the load on the pointed end of the screw k is relatively small, and a small wind vane, operable by comparatively small wind pressure, is suflicient to rotate the screw.

In the second case, the wedge angle is made slightly less than the critical angle so that when the restraining device has been unscrewed by the wind vane the tapered pin will remain in the locking position. However, under these conditions only a very small shock is necessary to cause the tapered pin to free itself leaving the striker free to ignite the detonator. With such an arrangement an extremely sensitive percussion fuse can be made which remains safe until the bomb or projectile to which it is at- In order to prevent the eflioiency of the wind I vane of an aerial bomb from becoming impaired by the action of moisture or the formation of ice thereon, as well as to prevent accidental premature operation of said wind vane, a protective and waterproof cover for the vane is provided, which cover is constructed and. mounted so as to be rapidly removed either manually or automatically immediately prior to or during release of the bomb from an aircraft. As shown, the wind vane is normally enclosed by a dome-shaped cover 1) whose outer edge is adapted to engage in the upwardly turned rim of a disc q surrounding and attached to the cap Z. The disc q carries spring retaining fingers 1', preferably three in number, which are shaped to engage above an internal beading s formed on the cover pwhich has thereby to be sprung into operative position. Surrounding the joint between the cover p'and the disc q is an india rubber sleeve t which is stretched into position so that it bears tightly against said cover and disc and thereby prevents entry of moisture or dirt through said joint. the apex of the cover a lug or eye u is provided for the attachment of a lanyard or other means for pulling the cover off the nose of the bomb and exposing the wind vane.

The above-described method of attaching the cover p enables it to be readily detached by a pull exerted at any operational angle. Any pull in a direction making a wide angle with the axis of the bomb will result in detachment of the cover by causing one of the spring retaining fingers r to act as a fulcrum. Detachment of the cover will leave the rubber sleeve t engaging the outer edge of the disc q but without any possibility of its interfering with the action of the wind vane.

The operation of the safety arming device will be apparent from the above description and the drawings. The safety pin o'having been Withdrawn, the cover p is pulled off as the bomb is released from the aircraft and the passage of the bomb through the air sets the wind 'vane in motion. For an initial predetermined period, which may be regulated by varying the setting of the wind vane upon the screw k, the vane merely turns upon the screw, but when the vane hub contacts the head of the screw the latter commences to turn with the wind vane, see Fig. 2. Thereafter, the continued rotation of the wind vane moves the screw to the inoperative position and if the tapered pin is designed to operate according to the first method set out above, the balls it gradually move inwards through the apertures 9 until the sleeve f is freed, whereupon the striker is impelled by the spring e upon the detonator d as shown in Fig. 3.

Should the tapered pin be designed to operate according to the second method set out above, the rotation of the wind vane will retract the screw it as above described but the tapered pin will remain in wedging contact with the balls until dislodged by the impact of the bomb with an objective or by a shock imparted by other means.

It will be observed that the present invention offers the advantage ofmaking it possible to adapt a single fuse ignition system for either of the two methods of operation above mentioned by the interchange of one part only, namely, the tapered pin.

Iclaim:

In a projectile, the combination of a casing having an annular abutment within the same, a detonator in said casing, means slidably mounted in said casing comprising a striker and a tubular portion, the latter having an annular series of openings through the wall thereof, spring means for driving said striker against said detonator, a pin having a tapered portion mounted for longitudinal movement in said tubular portion of said slidable means, the angle of taper of the tapered portion of which is slightly greater 'than the critical vangle of friction thereof, balls seated in said openings contacting the tapered portion of said pin and positioned,

when engaging the thicker portion of the taper, to engage said abutment and the upper surfaces bounding said openings to look said slidable means against movement, and to roll. off said abutment out of locking position when engaging the thinner portion of said tapered pin surface,

a screw-threaded spindle, threaded in the upper end of said casing, and bearing against the upper butt end of said pin, and a wind vane carried by said spindle, said spring means being sufilciently powerful to cause said balls by reaction against said abutment to squeeze said pin upwardly, out of locking position, during rotation vof said wind vane and upward movement of said spindle.

. HUGH CHARLES HEBARD. 

